Jonty Pearce gives a thorough breakdown of how to avoid other ships at sea, from tankers to trawlers

In days of yore coastal sailing largely revolved around establishing your position, meaning paper charts, hand-held compass bearings, transits, and navigation marks were your best friends.

Out of sight of land, if fortune really smiled on you, you might be able to access the modern technological wonders of the Decca Navigation System or LORAN-C, or just hope for a clear day for your sextant.

Everybody waved at each other, and the seas were largely deserted.

How times have changed! Today’s cruising sailor has GPS to pinpoint his position down to the last millimetre, but when out on our crowded seas, has to have eyes in the back of his head for pot buoys, wind farms, oil rigs, fishing vessels, ferries, commercial shipping traffic, military vessels, leisure craft, foiling yachts and hovercraft.

Not only that, but skippers need a detailed knowledge of Traffic Separation Schemes, exclusion zones and military ranges, Colregs and nautical electronics.

But fear not – with a basic understanding of today’s maritime challenges amateur sailors can still safely venture out and successfully sidestep all the different varieties of nautical coastal hazards.


With a basic knowledge of the rules of the road and a large dollop of common sense fellow sailing yachts and motorboats can easily be avoided.

Concentration levels might have to be at their maximum in the Solent during Cowes Week in comparison to cruising the Outer Hebrides out of season, but in a way it is easier to stay alert when there is plenty going on; more mishaps probably happen when crews are hunkered down behind the sprayhood in vile conditions on ‘empty’ seas.

The key is to keep a good lookout at all times and make sensible use of any electronic aids on board.

A different approach may be needed when encountering a fleet of racing yachts or dinghies; personally, I do not find their testosterone-fuelled aggression relaxing and although at times I might be classed the ‘stand on’ boat according to maritime rules, I’m happy to keep out of the way for a more enjoyable life.

Navigating busy waters

Racers may be best avoided if you want a quiet sail

With displacement-speed boats everything happens at a sensible rate.

The advent of foiling racers means that almost silent yachts and dinghies can appear in your personal space in the blink of an eye; their manoeuvrability might be limited and force them to hold their course to prevent catastrophe.

Fast planing craft can also become a threat in a short space of time, so be alert to speed; at 30kts a speeding boat will cover 1 mile in just 2 minutes.

A special consideration has to be made for canoeists, jetskis and paddleboarders.

Whilst usually seen close to shore, adventurous kayakers can be found crossing wide stretches of water; they are small, hard to see, and can cause an unexpected surprise.

Jetskis are frequently noisy and more noticeable, but, like paddleboarders, can venture into open water.

All these small craft are less noticeable when resting. Remember swimmers, and keep well clear of divers (see below).

Finally, keep your own speed down to sensible levels according to the situation.

Don’t pile on the revs in an anchorage; the occupants of the overloaded rubber dinghy with no freeboard will not bless you, and relaxed alfresco diners in their cockpits will curse you when your wake rocks over their wine glasses. Be nice.

Continues below…

A women using digital navigation on the deck of a yacht

8 tips for digital navigation

As with all aspects of navigation, following ‘best practice’ is the surest way to make sure you are passage planning…


Many professional water users go about their business in vessels of 30m length or less; tugs, pilot boats, a range of different sizes of fishing boats from large trawlers to pot boats, military range craft, diving boats, day trip boats, and small ferries.

While generally keeping a good lookout, we have all seen fishing vessels returning to port under autopilot with all the crew sorting the catch and tackle on the aft deck.

In many instances the double cone day signal for a vessel engaged in fishing is fixed on in an inappropriate permanent display.

Watch out for trawl lines reaching out astern of fishing boats – depending on the depth they can trail hundreds of metres behind. Look for fishing boats close together; they may be engaged in pair trawling.

If you get between them, your radio will probably deafen you with some choice language!

Other vessels provide a clue to events about to take place.

A pilot boat leaving harbour means a large ship is coming in. A cluster of tugs loitering together may mean a tanker is approaching. A potting boat bobbing about should heighten your lookout for pot buoys.


Navigating busy waters

Large vessels have severely limited manoeuvrability and may be constrained by their draught. Check where they are likely to turn

Navigating busy waters

In remote areas, relatively large vessels can operate close in shore

Navigating busy waters

Tugs milling around are a sure sign a big ship is incomin

My general adage when faced with large ships is to run away bravely.

Foolish is the short-lived sailor who pedantically adheres to the Colregs and expects a 300m LNG carrier with a deadweight of 100,000 tonnes to nimbly alter course to avoid his 30ft sailing yacht because his 1950 edition of the rules of the road suggests that he has ‘stand on vessel’.

Be realistic and reasonable, and have consideration for the drivers of these leviathans.

Remember above all things, that if you cannot see their bridge, they won’t be able to see you; even if there is an alert seaman on active lookout duty rather than glued to a radar screen in front of him who misses your tiny blip, a small yacht bobbing at the edge of visibility may easily not be seen.

These ships take miles to turn or slow down – respect is warranted.

Beware their speed; most container ships are designed to travel at 24kts. A ship that becomes visible on the horizon 12 miles away will be passing you in half an hour.

Not a good time to choose to go to the heads! At this speed they throw up a considerable wake – keep a good distance and don’t be too proud to alter course to cross their wash at a kinder angle.

The risk of collision can be assessed by electronic aids such as radar and Automatic Identification System (AIS), but don’t forget the old trick of using a hand-bearing compass or lining up a part of your own boat to see if the bearing of the other vessel changes; any constant bearing should alert you to a potential close quarters situation.

Areas of busy shipping use Traffic Separation Schemes to maintain control and segregation of shipping lanes; these can be complex and confusing for leisure sailors.

The rules state that your heading should be at right angles to the marked lane; note that leeway or tidal currents might mean that your course over the ground might not show up as perpendicular to the system.

Do the best you can, but remember they are monitored.

Navigating busy waters

Over 400 commercial vessels pass through the Dover Strait TSS every day; it is under full radar surveillance with penalties for infringements.

In 2012 a fishing vessel who travelled 17 miles in the wrong direction incurred a fine of £7,500 plus costs of £2,254.

You might not see him, but Big Brother is watching you.

Crossing these schemes is frequently not a relaxing pastime; with a never-ending line of speeding shipping, sailing yachts can feel like a rabbit in the headlights when picking their moment to creep across.

It’s even worse at night or in poor visibility; this is the time for the skipper to be alert, well rested, and on deck.

Other areas of concern include sailing past ports and areas of high congestion such as the Solent.

Check whether Port Control requires you to contact control by radio before passing, and be alert to the regular comings and goings of ferries around these areas.

In my home port we know to look out for the Irish Ferry at midday and 3pm; the port of Dover had 17,000 ferry entries last year.

Some port traffic can be fast; on the Portsmouth to Cherbourg route the high-speed catamaran Normandie Express can whisk 235 cars across the Channel at 42kts.

I suspect that the Solent must be every container ship captain’s nightmare.

Its winding channel jinks round the Bramble Bank and can be crammed with leisure craft; it has become one of the most notorious close quarters hotspots in the UK.

The combination of restricted forward visibility and limited manoeuvrability justifies the 1,000m moving prohibitory zone ahead of them.

Similar zones exist in other locations such as Milford Haven in front of its gigantic LNG carriers and tankers.

Those entering such ports should refresh their knowledge of the local regulations.

Vessels engaged in towing can pose particular confusion, especially at night.

A very experienced sailing friend was nearly caught out by a seemingly nonsensical combination of lights at night; hurried research clarified that the tow cable was surprisingly long, and he felt fortunate not to have gaily sailed into the cable between the two craft!

Remember that different styles of tow exhibit different lights – an alongside tow can be particularly confusing at night.

Chain ferries pose a particular hazard; the best known one is probably the ‘Bramble Bush Bay’ chain ferry that crosses the entrance to Poole Harbour between Sandbanks and Shell Bay.

The 74m vessel is dragged by chains across the swift currents between its slipways, announcing its departure by a flashing light and the raising of a black ball; take extra care at times of high tidal flow and when shipping is passing, and keep well clear of the chains!


Border Force, previously known as UK Border Agency, runs five cutters (mostly 42m) and six 20m coastal patrol RIBs.

Nearly half of their fleet are on patrol rotation in the English Channel watching for migrants, but their responsibilities also centre around general immigration, counterterrorism, and searching for illicit goods.

Their officers hold the powers of both Customs Officers and Immigration Officers, and it is proper to obey and cooperate with their requests.

Visually, their grey paint scheme is similar to Royal Navy vessels, though the outline differs.

The Royal Navy’s 75 vessels include aircraft carriers, submarines, destroyers, frigates, and patrol vessels.

The Royal Fleet Auxiliary has 13 ships with the backup of five Merchant Navy ships available to the RFA under a private finance initiative.

It is therefore not unusual to see Navy and associated ships in our seas; give them a good offing, and ensure you do not get in their way.

In port and at anchor keep as far away as practicable; they get twitchy when leisure vessels get too close.


As the years pass, more and more of our waters become denied to us.

Oil platforms require a safety exclusion zone of 500m around them; during construction, offshore wind farms request an Advisory Safety Zone of 500m – though in UK waters permanent safety zones are not expected to be established around wind farm groups once they are operational.

Ranges and military zones can restrict passage, and ports may harbour restricted sectors.

When planning a voyage, mariners should assess all risks in the proximity of wind farms: they are usually in shallow water and could, over time, affect the depth of water through scouring of the seabed.

Local tidal streams can be altered, and rotor effects can change the flow of the wind and its impact on a vessel.

While sailing through turbine areas is legal, many sailors prefer to alter their passage plan to avoid them.

I sail in Milford Haven, a port with regular LNGC (liquefied natural gas carrier) traffic whose exclusion zone in the channel extends ahead to the limit of line of sight from the bridge (basically as far as a patrol vessel) and 100m astern (usually marked by an escort tug).

Boaters should also keep 100m off refinery berths. These vessels are immense, and even smaller tankers seem huge in the relatively narrow channel.

Keep well clear, and make your intentions crystal clear; you do not wish to be the target of the five horn blasts of shame.

An important coastal passage eastward from Milford Haven can be temporarily closed to passing craft when the Castlemartin Range is active.

Live firing can take place for up to 44 weeks of the year (though not usually at weekends); the coastal exclusion zone can reach as far as 12 miles or as little as 3 miles off the coast depending on the weapons and ammunition being used.

The firing times are well published online, and announced on VHF.

Safety patrol vessels remind those unaware of the danger. Dorset’s Lulworth Range is another example of coastal ranges that limit sea traffic; in fact, any passage plan round the UK’s shores should consider military ranges and their firing times.

Even the wilds of Cardigan Bay can be enlivened by MOD Aberporth’s activities.

Other areas of restriction include Submarine Exercise Areas. In the Hebrides, The Minch is a popular area for submarine exercises, though charted potential zones stretch south from the Butt of Lewis right down to North Channel between Ireland and southern Scotland.

Major exercises can include significant surface craft activity, though Stornoway and Belfast Coastguards add their own warnings as well as announcements on VHF weather forecasts.

My own Penguin Cruising Club’s much missed late Commodore and founder was an ex-naval man; on one occasion sailing The Minch he opted to cross a submarine exercise area to catch up with the rest of the fleet.

Initially, the VHF had not been turned on, but when this was remedied halfway across, the radio immediately crackled into life with an irate Naval communique; Kevin’s response was, ‘Commander Walton here. We’re just crossing, won’t be a moment. Out.’

He then turned off the set, earning the club’s history a notorious memory.

This is not a practice to be recommended.


Pot buoys are probably the stationary object that causes most grief to yachtsmen.

Small, unlit and frequently poorly marked, they can be as numerous as moths round a camping light in some areas, and I have seen them neatly placed in the middle of a marked channel.

I have either run over them or had a near miss in all the waters I sail.

A companion boat even became tethered to the seabed by one halfway between Fair Isle and Orkney.

They are also tiresome when placed in marked anchorages and narrow channels.

A wetsuit, neoprene hat, goggles, flippers, and a sharp hacksaw on a lanyard are now part of my on-board kit.

Whilst petitions have been made for legislation enforcing better marking of the buoys, currently all we can do is keep a sharp lookout and fit a rope cutter.

Sailing, (especially) motoring, at night is a special concern in their breeding grounds; even with a bright searchlight they can be all but invisible.

Unbelievably, navigational buoys themselves can also be hazardous.

Navigation mark

Navigation marks can be a hazard, particularly if you use their location as a waypoint, coupled with an autopilot

Sound advice is never to use the recorded positions of buoys as waypoints for an autopilot route; such is the accuracy of modern electronics that arrival at such a waypoint can be announced by a loud impact.

A while back there was the story of a million-pound-plus brand-new motor cruiser on a delivery trip whose skipper had inadvisably fallen foul of this very practice; the collision with the large floating waypoint split the hull in two.

Make sure you place your waypoints in open water, and when in the vicinity of navigational marks ensure you avoid being swept down onto them by unexpected tidal currents – they can really mess up your gelcoat.

I have already mentioned wind farms and oil rigs, but fish farms, mussel farms, and oyster farms can also pose inshore problems.

Oyster Farm

Static obstructions like this oyster farm should be marked on charts

Mussel Farm

A mussel farm should be well buoyed, but don’t try sailing through it

While usually well marked on charts, they tend to be placed in the same sheltered areas that we might choose for anchorage.

Floating fish farms can be quite extensive but are easily seen and avoided; likewise the extensive network of buoys supporting mussel culture zones, though they too can interrupt an inshore route.

Oyster farms can rely on the construction of frames or posts on the seabed; they are generally installed on drying ground but may not be evident at high water.


While not strictly stationary, recreational and professional divers and their support boats remain fairly immobile.

Divers can surface, drift, or swim some distance from the diving boat, so give them a proper clearance.

Identification should be by the display of International Code flag ‘A’, though it is worth pointing out that North America uses a red flag with a white stripe just to be different.

At night, signal lights for vessels restricted in their ability to manoeuvre are displayed, though I imagine few leisure divers choose to be in the water in the dark.

Finally, no article on avoiding coastal hazards could be complete without mentioning rocks.

While they are generally well marked, there are exceptions; the Stockholm archipelago is home to so many rocks that some have escaped formal identification.

The idyllic anchorage of Tinker’s Hole lies on the west coast of Mull; a notorious rock sits in the entrance channel.

Although it is well marked on the chart it seems to be both easily forgotten and magnetic – our club call it Penguin Rock because so many of our skippers have fallen foul of it.

Chart detail loaded into chartplotters can either be hidden due to inadequate zooming in or erroneously placed; small-scale paper charts are generally considered safer.

Many rocks are unmarked, though unofficial marks such as small buoys or plastic milk cartons are intended as a warning; official marks are beneficial but remember they can be carried away in storms. Jack and Ramsey Sounds in Pembrokeshire are both home to well charted rocks and reefs.

While easily avoidable at slack water, 6knots of spring tide can sweep inexperienced skippers perilously close to them.

It’s always a good idea to accord rocks considerable respect!



The world becomes a different place when you can’t see where you’re going.

Avoiding shipping and other floating or fixed hazards becomes an uncertain challenge, but the Colregs provide a framework for sailors to work with; all skippers should be fully conversant with Section III (Conduct of vessels in restricted visibility) and as proficient at recognising the combinations of lights and sound signals as they are for day shapes.

Sailing at night can be a peaceful and memorable experience heightened by phosphorescence, sparkling stars and the coded flash of navigation marks in front of the loom of distant lighthouses.

However, sailing in the dark can also be confusing; a night-time entry of a port such as Milford Haven can cause sensory overload unless a clear plan detailing a list of consecutive lights to tick off is adopted.

Lights displayed by both vessels and navigation marks can easily be lost or distorted by the background of shore illumination; that puzzling south cardinal might be a car’s headlights passing behind a line of roadside trees.

Unlit objects can pose problems too; boats on moorings, empty moorings, pot buoys and floating lines and debris are frequently invisible.

A bright searchlight is useful to have on board, but runs the risk of trashing your carefully nurtured night vision.

Reduced visibility and fog hampers identification of all features and objects.

While good visibility is defined as being able to see more than 5 miles, moderate visibility reduces that to between 2 and 5 miles, poor drops it to between 1,000m and 2 miles.

Very poor visibility is defined as less than 1,000 metres, though in dense fog you might not be able to discern your outstretched hand.

Crowded AIS

AIS display showing a very crowded Singapore Strait

Few seamen would choose to go out in fog, but if you are caught out the following steps can help:


  • Turn on navigation lights (they might just help)
  • Post lookouts on the bows (and change them frequently)
  • Ensure all crew are wearing lifejackets
  • Have the engine ready for use (warmed up)
  • Hoist radar reflector unless permanently aloft
  • Operate your radar, if fitted
  • Watch your AIS screen, if fitted
  • Plot a fix as soon as you realised visibility is reducing
  • Maintain good navigation and records
  • Monitor the VHF, especially the port control channel
  • Avoid busy waterways and harbours with a lot of shipping
  • Change your route or destination to an area with no dangers
  • Stay in shallow water – ships are unlikely to follow! Consider anchoring
  • Monitor the depth constantly
  • Follow a contour line, if possible, into your chosen haven

Sound travels surprisingly far in fog, though pinpointing the source can be very difficult.

Although the wind generally drops when conditions are foggy, sailing (if possible) enhances auditory clues that can be masked by your own engine.

If motoring is imperative, it can be worth stopping the engine periodically for a sound check.

Even so, there are few things more ominous than the hum and thump of an invisible passing ship whose engine seems to come from all round you.

This is when boats that have not installed electronic aids such as AIS and radar wish that they had.


There are three main electronic resources that can help leisure yachtsmen seek, identify, and avoid shipping.

None of them are a panacea, and many sailors choose to fit all three and then use them according to circumstances in order to avoid excessive battery drain when not under engine.


It takes a bit of practice to properly understand radar


Radar Target Enhancers made by the likes of Echomax; with a current draw of only around 10mA they can be left on all day, and the control box can be switched to give an audible warning if the enhancer is ‘painted’ by another vessel’s radar.

They can be mounted at the pushpit (range 6-8 miles), suspended from the rigging, or installed at the mast top (range as much as 25 miles).

Masthead mounting has the disadvantage of ‘seeing too far’; when the unit detects that a distant ship has illuminated your yacht with its radar an audible warning is triggered.

However, that distant ship might be beyond the range of your own radar, causing unnecessary angst.

The temptation then is to silence the alarm at night in order not to disturb sleeping crew, thereby rather defeating the object of fitting the kit in the first place.

A 2-3m mount height gives a more useful warning of vessels visible on the horizon, with the subsequent option of using an AIS Multi-Function Display (MFD) to track them.

AIS comes in receive-only and transmit/receive units. The receive-only unit can warn of other AIS-transmitting craft up to 20 miles away and display them on a screen or MFD.

They are of benefit for detecting commercial and large vessels that must transmit AIS by law, but many smaller craft, yachts, and fishing vessels either do not have the equipment installed or choose not to transmit their position.

Investing in a unit that also transmits your own AIS position can both warn receiving vessels of your existence and give them the option to avoid you or call you up on their DSC radio using your MMSI number; those fitted with both a receive-only unit and a DSC radio can do likewise.

AIS units sip genteelly at the battery, though if viewed through an MFD chartplotter the consumption is higher.

Radar is the most power-hungry option but is able to reveal targets well over the horizon at up to 24 miles that can be tracked from a distance of 12 miles.

Guard zones can be set which signal the proximity of another vessel.

However, few cruising yachts enjoy the reserves of battery power necessary to support a continuously transmitting radar and its MFD; they are therefore often only used for short periods.

New generation broadband radar units use less power but would still need a relatively amp-hungry chartplotter to reveal their probings.

Radar has the advantage of being able to display coastal features and craft not fitted with AIS transmitters.

MAIB advice


Make sure everybody knows what to do in an emergency. Include raising the alarm in all safety briefs, especially with crew who are new to the boat. Explain which buttons to press on the VHF and chart plotter, and what they must do next. Always nominate a second in command in case you are the one who’s in trouble.


Ensure all crew are familiar with their lifejacket, both for their own benefit and if they need to retrieve someone from the water. Unpack one so that crew can understand how they inflate and see what’s inside, especially the lifting strop, not to be confused with the harness D-ring. Explain the vital part played by the crotch straps.


Prepare thoroughly for gybes – both planned and accidental. Many of the injuries and worse, reported to the MAIB involve crew being struck by the mainsheet rather than the boom.


Always be on the lookout. Shipping in UK coastal waters is dense and collisions with small craft are too frequent. Remember, their relative speed will be a good deal higher than your own.


Going aground isn’t a normal activity when coastal sailing. After a grounding ensure all is well – this usually involves an inspection by an expert. Keel failures are as catastrophic as wing failures on aircraft.

There is no doubt that the most useful and reliable bit of kit is the Mk1 eyeball and Mk1 ear.

To augment these the following can be of use, and it is a good idea to check their presence and operation before setting out on any trip:

  • Binoculars
  • Searchlight/torch
  • Foghorn
  • Hand-bearing compass
  • Correct navigation light
  • Familiarity with the VHF/DSC radio
  • Function of any fitted radar/AIS unit
  • GPS chartplotter/back-up paper chart availability
  • Maintenance of a detailed log
  • Lifejacket and tether options
  • Adequate fuel, water, gas, food and spares
  • Appropriate warm and waterproof clothing

All crew on board should pay attention to a pre-cruise briefing that covers the yacht’s functions and emergency procedures. This list is far from comprehensive, but a skipper who is prepared is a skipper ready to take on the joys and trials of sailing the coastal waters round our beautiful island group. Enjoy!

Jonty Pearce

Jonty Pearce is a lifelong cruising yachtsman and retired GP. He keeps his Southerly 105 ketch Aurial in Milford Haven.